Faculty and students in the East Carolina University (ECU) Department of Construction Management have been working with S.T. Wooten and the N.C. Department of Transportation to explore the possibility of using the polymer fibers in recycled masks in hot mix asphalt.
Researchers hope that the addition of the recycled masks will help the asphalt resist rutting—the permanent deformation of pavement that can occur as vehicles drive on the same areas on roadways repeatedly.
The process involves shredding the masks and adding the material to the hot mix asphalt by .25 percent to 1.5 percent of the total weight. With paving conducted at up to 300 degrees, the plastic in the masks becomes a fluid and acts as a binding agent that hardens and stiffens as it cools.
The addition of the recycled masks is projected to help reduce road rutting, which is caused by traffic volume, tire pressure and axial load and often emerges in the first few years after a road is paved.
“Rutting is the major distress of asphalt pavement and happens on some major intersections along the wheel path,” says Dr. George Wang, chair of the Department of Construction Management and one of those involved in the study. “It can cause accidents with water ponding in the rut and in wintertime when water in the rut freezes.”
So far results of testing in the N.C. Department of Transportation’s Asphalt Pavement Analyzer appear favorable, with the sample asphalt exhibiting “excellent to very good resistance to permanent deformation,” according to the report.
Wang says that while the state allows a maximum rut depth of 11.5 millimeters for local roads and 4.5 millimeters for interstate highway pavement, testing of various mixtures with the recycled masks show a rut depth range of .9 to 3.2 millimeters.
“With the increase in content of fiber, the rut decreases,” Wang notes. “That means that this mix is designed for local roads, and because of the fiber addition, it can be used as higher grade road pavement.”
Wang, associate professor Dr. Carol Massarra, teaching assistant professor Dr. Jodi Farrington, teaching instructor Chelsea Buckhalter and graduate student Hasibul Hasan Rahat are conducting the research.
The group plans to continue working with the Department of Transportation and S.T. Wooten to conduct more extensive testing and possibly funded research on the use of mask and similar nonstructural fibers in asphalt. They are also working on publishing the results of the initial testing, according to ECU.